1. Field of the Invention
The present invention relates to a method for manufacturing a color selection electrode structure used for television, computer displays, and the like, and a color cathode ray tube having the color selection electrode structure.
2. Description of the Related Art
In general, a color cathode ray tube has a color selection electrode structure including a color selection electrode for carrying out color selection with respect to three electron beams emitted from an electron gun and a frame for holding the color selection electrode.
Recently, for the color selection electrode structure, a tension mask such as a one-dimensional tension mask and a two-dimensional tension mask, etc. has been employed. Such tension masks are formed by stretching and welding the color selection electrode onto the frame in a state in which tension (tensile force) is applied to a color selection electrode, which is a flat plate member having a large number of apertures, in one direction or both directions from the shorter axis and the direction of the longer axis of the color selection electrode.
For example, as shown in FIG. 7, a color selection electrode structure 100 of the one-dimensional tension mask is manufactured as follows. That is, a color selection electrode 103 having a plurality of apertures 102 is stretched in the direction of the shorter axis (in the direction shown by an arrow 104) in a state in which a frame 101 is pressed and deformed, and welded and fixed onto the frame 101, followed by releasing the pressure applied to the frame 101 so as to apply tension to the color selection electrode 103. Thereafter, an elastic supporting body 105 is welded and fixed onto the frame 101 to which the color selection electrode 103 is held with stretched.
Then, the color selection electrode structure 100 is incorporated into a panel (not shown in the drawings) of the color cathode ray tube after the heat treatment at 450° C. for removing any distortion that remained on the welded portion of the color selection electrode structure 100.
However, in a conventional method for manufacturing the color selection electrode structure 100, the color selection electrode structure 100 formed by stretching with tension applied had problems due to variation in strength depending upon materials of the frame 101 and the color selection electrode 103 and variation in the tension amount of the individual color selection electrode structures 100 depending upon the accuracy in the apertures 102 provided on the color selection electrode 103 or the processing accuracy of the frame 101, etc. Furthermore, by the subsequent heat treatment, because the change of the material property is added due to the high temperature creep, the variation in the tension amount becomes larger.
Some of the color selection electrode structures 100 cannot obtain the necessary tension amount. When the color selection electrode 100 cannot obtain the necessary tension amount and the tension amount is small, if shock, etc. is applied from the outside to the color selection electrode structure 100, the vibration of the color selection electrode 103 is increased. Therefore, in a color cathode ray tube using the color selection electrode structure 100 having a small tension amount, the defect of color misalignment occurs, which may cause deterioration of the quality of a color cathode ray tube.
The presence of the color selection electrode that cannot sufficiently obtain the tension amount may cause the relative deterioration of the quality of the color selection electrode structure and in turn the deterioration of the color cathode ray tube. Consequently, the reliability of a color selection electrode and the color cathode ray tube as a product may be deteriorated.
Therefore, in the manufacturing process of the color selection electrode structure, although it is important to measure and understand the tension amount applied to the color selection electrode structure in order to maintain the reliability and the quality of the color selection electrode, no useful means for measuring the tension amount of the color selection electrode structure have been available.